<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
</head>
<body>
    <script>
      var a={n:1};
      var b=a;
          a.m=a={m:2};
      console.log(a);//{m:2}
      console.log(b);//{m:{m:2},n:1}
      //赋值运算从右向左执行
    </script>
</body>
</html>